Abstract:The plant communities on the wetlands of an agricultural landscape in central Italy were studied. Indicator species, dominant life forms, alien species cover and prevailing habitat conditions (using Ellenberg indicator values) were shown to characterize the four groups that emerged from a classification analysis. 31 vegetation units were documented by 98 original phytosociological relevés and a floristic, synecological and distributional description was presented with syntaxonomic notes for each unit. A new association, Rorippo amphibiae-Potentilletum reptantis, was described. The high phytocoenotic diversity, the 7 coenoses belonging to habitat of Community or regional interest and the higher risks affecting these wetlands in an anthropic countryside (eutrophication, invasion of alien species, human modifications of the landscape) underline the fact that these wetlands are of high conservation value and the goal of protecting this very important environment.

We propose a method to assess the distribution of plant assemblages along rivers delimiting homogeneous fluvial types using cluster analysis applied to morphological features, quantified with aerial photos and geographic information system software. A stratified random sampling design along the elevational gradient was used to analyze riparian plant species. Multivariate statistics were applied to detect patterns of variation in the species data, and among functional and ecological groups. Cluster analysis identified four fluvial types: headwater, low sinuosity, braided, and incised. Canonical Correspondence Analysis, INdicator SPecies ANalysis, and partial ordinations all suggested that fluvial types were characterized by well-defined indicator species. The differences found by Redundancy Analysis and nonparametric analysis of variance for functional and ecological groups also supported the fluvial type division, showing different distributional trends for annual and woody species, and the greatest ecological distance between braided and headwater types. Based on the ordination results, dividing fluvial types according to morphological features was justified by environmental and floristic differences, although plant species variability was only partially described. Our results illustrated that the fluvial type classification created using this methodology was consistent with natural plant species distribution patterns.

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Landi M. and Angiolini C. 2008. Habitat characteristics and vegetation context of Osmunda regalis L. at the southern edge of its distribution in Europe. Bot. Helv. 118: 45 -57.The abundance of Osmunda regalis was investigated in 42 natural populations in central Italy in order to (i) test which habitat characteristics correlate with its abundance at regional scale and at local scale, and (ii) identify the optimal habitats for the species in a Mediterranean area. This knowledge may contribute to the effective conservation of O. regalis, which is under threat in Italy. Ramets (rosettes of fronds) were counted in several plots of 25 m 2 within each population and related to habitat characteristics as well as plant species composition using univariate and multivariate statistics. The abundance of ramets at regional scale was positively correlated with mean annual precipitation and altitude. Large populations mainly occurred at sites with northeastern exposure, i.e. a cool and humid microclimate. The density of ramets at local scale was negatively correlated with rockiness, stoniness and shrub cover. Vascular plant species associated with high density of O. regalis were pioneer species typical of open woods and stagnant waters. Spring swamps therefore represent the habitat with the most favourable edaphic, microclimatic and vegetational conditions for the species at the southern edge of its distribution in Europe, where the limiting factor is the annual water availability.